Acetylcholine receptors of thoracic dorsal midline neurones in the cockroach, Periplaneta americana

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Abstract
The actions of acetylcholine and cholinergic ligands have been studied using dorsal midline neurones from the metathoracic ganglion of the cockroach Periplaneta americana. Both nicotine and oxotremorine depolarized dorsal midline neuronal cell bodies. Dose‐response curves for nicotine and oxotremorine saturated at different levels. Nicotine‐induced depolarizations were completely or partially blocked by mecamylamine, d‐tubocurarine, strychnine, and bicuculline, but were insensitive to α‐bungarotoxin (100 nM), atropine (100 μM), scopolamine (10 μM), and pirenzepine (50 μM). Following pretreatment with collagenase, the dorsal midline neurones were sensitive to high doses of α‐bungarotoxin (3 μM). Oxotremorine‐induced depolarizations were blocked by scopolamine (10 μM), atropine (100 μM), and pirenzepine (50 μM) and were insentive to mecamylamine (10 μM) and d‐tubocurarine (100 μM). The results indicate the coexistence of at least two distinct acetylcholine receptors on dorsal midline neuronal cell bodies in the cockroach metathoracic ganglion.